Analysis of differential metabolites and metabolic pathways of mono- and inter-cropped wheat in response to Blumeria graminis f. sp. tritici infection
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摘要: 为了解单作、间作小麦响应白粉病侵染的代谢差异, 揭示间作提高小麦抗白粉病的生理机制, 本文通过盆栽试验设置 75 mg∙kg−1 (N1)、150 mg∙kg−1 (N2)、225 mg∙kg−1 (N3) 3个施氮水平, 研究接种白粉病病原菌后, 小麦单一种植和小麦蚕豆间作下白粉病的发病情况, 并通过广泛靶向代谢组学分析单作、间作小麦响应白粉病菌侵染的差异。结果表明: 氮水平和氮水平×种植模式显著影响小麦白粉病发病率和病情指数; 在3个氮水平下, 间作降低白粉病发病率25.54%~38.81%、降低病情指数20.11%~21.97%, 其中低氮水平控制效果较好。白粉病菌侵染后, 单作、间作小麦叶片中共检测到822种代谢产物, N1、N2和N3水平下分别发现差异代谢物69种、52种和88种。KEGG代谢通路分析发现单间作小麦差异代谢物主要富集在氨基酸的生物合成、代谢途径和次生代谢物的生物合成。其中N1和N2水平下, 差异代谢物富集在代谢途径, N1和N3水平下差异代谢物富集于氨基酸的生物合成。进一步对上调、下调差异倍数前10的代谢物分析发现, 与单作相比, N1水平间作上调了谷胱甘肽还原型、L-色氨酸、L-天冬酰胺和L-谷氨酰胺, N3水平间作上调了L-天冬酰胺、L-高甲硫氨酸和L-色氨酸。除此之外, 少数生物碱类、酚酸类和有机酸类等代谢物质在氮胁迫下也呈现不同程度的变化。总之, 单作和间作小麦响应白粉病病菌侵染的应答过程受氮水平调控。在白粉病病菌侵染中, 间作调控差异代谢物如氨基酸及其衍生物类、生物碱类、酚酸类和有机酸类等在植物体内的变化, 可能是间作提高小麦白粉病抗性的机制之一。其中, 氮胁迫条件下间作调控氨基酸及其衍生物与小麦白粉病抗性提高密切相关。Abstract: Wheat and faba bean intercropping can alleviate the occurrence and severity of wheat powdery mildew. However, the physiological mechanism of intercropping improving wheat disease resistance remains unclear. This study aimed to understand the metabolic differences between mono- and inter-cropped wheat in response to Blumeria graminis f. sp. tritici infection and reveal the physiological mechanism of intercropping for improving wheat resistance to powdery mildew. In this study, the following three nitrogen (N) application levels were established: 75 mg·kg−1 (N1), 150 mg·kg−1 (N2), and 225 mg·kg−1 (N3). Following inoculation with B. graminis f. sp. tritici, the occurrence of powdery mildew in mono- and inter-cropped wheat was investigated, and the metabolomics of mono- and inter-cropped wheat in response to infection with B. graminis f. sp. tritici were analyzed by UPLC-MS/MS, using a widely targeted metabolomic method. The results showed that N levels and N levels × planting patterns significantly affected the incidence and disease indices of powdery mildew in wheat. Under all three N levels, wheat intercropping with faba bean reduced the incidence of wheat powdery mildew by 25.54%–38.81% and decreased the disease index by 20.11%–21.97% relative to mono-cropped wheat (MW), and the intercropping control effect under the N1 level was better than that under N2 and N3 conditions. A total of 822 differential metabolites were detected in the mono- and inter-cropped wheat leaves, of which 69, 52, and 88 were detected at the N1, N2, and N3 levels, respectively. Intercropping of wheat and faba bean regulated flavonoids, alkaloids, amino acids and derivatives, and phenolic acids in wheat leaves compared to MW. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of differential metabolites showed that they were mainly enriched in the biosynthesis of amino acids, metabolic pathways, and secondary metabolites. Among them, metabolites with significant differences were enriched in metabolic pathways at the N1 and N2 levels, and metabolites with significant differences were enriched in amino acid biosynthesis under N stress conditions (N1 and N3). Further analysis of the metabolites from the top 10 up- and down-regulated genes revealed that intercropping upregulated glutathione (G-SH), L-tryptophan, L-asparagine, and L-glutamine in wheat leaves at the N1 level relative to MW, and upregulated L-asparagine, L-homomethionine, and L-tryptophan in intercropped wheat leaves at the N3 level relative to MW. In addition, a few metabolites, including alkaloids, phenolic acids, and organic acids, in wheat leaves were regulated by intercropping compared with MW under the N1 and N3 levels. In conclusion, the response of wheat to powdery mildew infection was regulated by N levels. Metabolites involving amino acids and derivatives, alkaloids, phenolic acids, and organic acids in wheat leaves are regulated by intercropping during B. graminis f. sp. tritici infection and induce different physiological reactions, possibly being one of the mechanisms by which intercropping improves wheat powdery mildew resistance. Intercrop-regulated amino acids and their derivatives under N stress are closely associated with wheat powdery mildew resistance. The present study identified the different responses of mono- and inter-cropped wheat to disease infection via metabolic analysis, facilitating a comprehensive understanding of crop diversity for the management of pests and diseases.
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图 6 单间作小麦在不同施氮水平的差异代谢物的层次聚类图
图A、B、C分别表示75 mg∙kg−1 (N1)、150 mg∙kg−1 (N2)和225 mg∙kg−1 (N3)施氮水平下单作、间作之间的比较。MW表示单作小麦, IW表示间作小麦。Figure A, B and C show the comparison between mono- and inter-cropped wheat at nitrogen application levels of 75 mg∙kg−1, 150 mg∙kg−1 and 225 mg∙kg−1, respectively. MW and IW represent the mono- and inter-cropped wheat, respectively.
Figure 6. Hierarchical cluster diagrams of differential metabolites of mono- and inter-cropped wheat at different nitrogen application levels
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图 1 与蚕豆间作和施氮水平对小麦白粉病发生的影响
MW和IW分别表示单作小麦和间作小麦, N1、N2和N3分别表示施氮量为75 mg∙kg−1、150 mg∙kg−1和225 mg∙kg−1; *表示同一氮水平同一时间不同种植模式间差异显著(P<0.05)。MW: mono-cropped wheat; IW: inter-cropped wheat. N1, N2 and N3 are nitrogen application levels of 75 mg∙kg−1, 150 mg∙kg−1 and 225 mg∙kg−1, respectively. * indicates significant difference between different planting patterns under the same N level at the same sampling time (P<0.05).
Figure 1. Effects of intercropping with faba bean and nitrogen application level on powdery mildew occurrence in wheat
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图 2 不同施氮水平下单间作小麦叶片代谢物主成分分析
MW和IW分别表示单作小麦和间作小麦, N1、N2和N3分别表示施氮量为75 mg∙kg−1、150 mg∙kg−1和225 mg∙kg−1。
Figure 2. Principal component analysis of leaves metabolites of mono- and inter-cropped wheat at different nitrogen application levels
MW: monocropped wheat; IW: intercropped wheat. N1, N2 and N3 are nitrogen application levels of 75 mg∙kg−1, 150 mg∙kg−1 and 225 mg∙kg−1, respectively.
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图 3 不同施氮水平下单间作小麦叶片代谢物正交偏最小二乘法-判别分析得分图(A、B、C)与置换模型检验图(D、E、F)
MW和IW分别表示单作小麦和间作小麦, N1、N2和N3分别表示施氮量为75 mg∙kg−1、150 mg∙kg−1和225 mg∙kg−1。R2X和R2Y: 模型对X和Y矩阵的解释率; Q2: 模型的预测能力。MW: mono-cropped wheat; IW: inter-cropped wheat. N1, N2 and N3 are nitrogen application levels of 75 mg∙kg−1, 150 mg∙kg−1 and 225 mg∙kg−1, respectively. R2X, R2Y: interpretation rate of the model for X and Y matrix; Q2: predictive power of models.
Figure 3. Orthogonal partial least squares method-discriminant analysis score maps (A, B, C) and displacement model test maps (D, E, F) of leaf metabolites in mono- and inter-cropped wheat at different nitrogen application levels
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图 4 不同施氮水平下单间作小麦叶片差异代谢物Venn图
N1-MW vs N1-IW: N1水平(施氮量为75 mg∙kg−1)下单作、间作小麦之间差异物的比较; N2-MW vs N2-IW: N2水平(施氮量为150 mg∙kg−1)下单作、间作小麦之间差异物的比较; N3-MW vs N3-IW: N3水平(施氮量为225 mg∙kg−1)下单作、间作小麦之间差异物的比较。N1-MW vs N1-IW: comparison of differential metabolites between mono- and inter-cropped wheat at nitrogen applicaiton level of 75 mg∙kg−1 (N1 level); N2-MW vs N2-IW: comparison of differential metabolites between mono- and inter-cropped wheat at nitrogen applicaiton level of 150 mg∙kg−1 (N2 level); N3-MW vs N3-IW: comparison of differential metabolites between mono- and inter-cropped wheat at nitrogen applicaiton level of 225 mg∙kg−1 (N3 level).
Figure 4. Venn diagram of differential metabolites in mono- and inter-cropped wheat leaves at different nitrogen application levels
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图 5 单间作小麦在不同施氮水平的差异代谢物KEGG分类和富集图
图A、B、C分别为75 mg∙kg−1、150 mg∙kg−1和225 mg∙kg−1施氮水平下单作、间作小麦之间差异代谢物分类图(左)和富集图(右)。Figures A, B and C show the classification (left) and enrichment (right) of different metabolites between mono- and inter-cropped wheat at nitrogen application levels of 75 mg∙kg−1, 150 mg∙kg−1 and 225 mg∙kg−1, respectively.
Figure 5. KEGG classification and enrichment of differential metabolites in mono- and inter- cropped wheat at different nitrogen application levels
表 1 不同发病时期的氮水平、种植模式和氮水平×种植模式对小麦白粉病发病率和病情指数的影响
Table 1 Effects of nitrogen level, planting pattern and nitrogen level × planting pattern on incidence and disease index of wheat powder mildew in different disease periods
接种后天数
Days after
inoculation (d)相关项
Related item氮水平
N level
(N)种植模式
Cropping pattern
(C)N×C 3 DI * ns ns DSI ** ns * 4 DI ns ns ns DSI * ns ns 5 DI * ** ** DSI ns ** *** 6 DI * ns *** DSI * ns ** 7 DI * * *** DSI ** ns * 8 DI * ns ** DSI * ns ** 9 DI ** * *** DSI ** ns ** 10 DI * ns * DSI ns ns ns *: P<0.05; **: P<0.01; ***: P<0.001; ns: 不显著。DI: 发病率; DSI: 病情指数。*: P<0.05; **: P<0.01; ***: P<0.001; ns: not significant. DI: incidence rate; DSI: disease index. 
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表 2 不同施氮水平下单间作小麦叶片差异代谢物分类
Table 2 Classification of differential metabolites of leaves of mono- and inter-cropped wheat at different nitrogen application levels
分类
ClassN1-MW vs N1-IW N2-MW vs N2-IW N3-MW vs N3-IW 上调
Up下调
Down总体
Total上调
Up下调
Down总体
Total上调
Up下调
Down总体
Total黄酮 Flavonoids 2 1 3 5 0 5 0 9 9 萜类 Terpenoids 0 0 0 1 0 1 1 0 1 有机酸 Organic acids 3 5 8 0 5 5 5 5 10 生物碱 Alkaloids 21 1 22 3 3 6 10 10 20 氨基酸及其衍生物 Amino acids and derivatives 14 1 15 1 5 6 11 0 11 酚酸 Phenolic acids 2 3 5 0 7 7 2 21 23 木脂素和香豆素 Lignans and coumarins 2 0 2 0 2 2 0 3 3 脂质 Lipids 2 2 4 1 1 2 0 0 0 核苷酸及其衍生物 Nucleotides and derivatives 5 5 10 0 15 15 1 2 3 鞣质 Tannins 0 0 0 0 0 0 0 1 1 其他 Others 0 0 0 1 2 3 0 7 7 合计 Total 51 18 69 12 40 52 30 58 88 N1-MW vs N1-IW: N1水平(施氮量为75 mg∙kg−1)下单作、间作小麦之间差异物的比较; N2-MW vs N2-IW: N2水平(施氮量为150 mg∙kg−1)下单作、间作小麦之间差异物的比较; N3-MW vs N3-IW: N3水平(施氮量为225 mg∙kg−1)下单作、间作小麦之间差异物的比较。N1-MW vs N1-IW: comparison of differential metabolites between mono- and inter-cropped wheat at nitrogen applicaiton level of 75 mg∙kg−1 (N1 level); N2-MW vs N2-IW: comparison of differential metabolites between mono- and inter-cropped wheat at nitrogen applicaiton level of 150 mg∙kg−1 (N2 level); N3-MW vs N3-IW: comparison of differential metabolites between mono- and inter-cropped wheat at nitrogen applicaiton level of 225 mg∙kg−1 (N3 level).
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